The central focus of this Program Project is the role of immune mediated inflammation in the development of chronic arthritis and how that inflammation can be regulated. In spite of a preponderance of evidence linking immunity and chronic inflammatory arthritis, in particular rheumatoid arthritis, there is a lack of data on how that immune response is initiated, what factors determine how it will progress, why it becomes chronic, and how chronic inflammation can be resolved without long term immunosuppression. This project will use a combination of mouse models of inflammatory arthritis to address these questions. It proposes an ambitious but highly focused approach incorporating three interrelated projects supported by a core. No animal model perfectly mimics human rheumatoid arthritis; however, they can reproduce important aspects of disease including pathways that are important for joint inflammation and destruction. Animal models have been invaluable in providing an in vivo platform for testing of therapeutic approaches to regulate disease. By analyzing uniquely different models, this project will provide a more integrated approach to elucidation of the pathogenesis of arthritis and overcome the limitations of any single model. In particular the Program will address how innate immune reactions can be regulated. Innate immune reactions are part of the body's first line of defense in protection against bacteria and other invaders. It is thought that arthritis may be triggered by exposure of susceptible individuals to commonly encountered bacterial components. It has recently been discovered that protein kinase D1 (PKD1) is a key intermediary in a critical signaling pathway in that response. This intermediary acts by shuttling other molecules into lipid rafts on the cell surface. If the interaction of PKD1 with these molecules can be interrupted, arthritis may be prevented. A novel method for accomplishing this interruption using decoy peptides is proposed. Once inflammation and arthritis have developed, they are perpetuated by ongoing autoimmune reactions. Several autoantigens have been identified that may be responsible for this process but the relative importance of particular reactions has been difficult to establish. One way to ascertain the contribution of a particular reaction is by specific downregulation. Using humanized mice that are transgenic for rheumatoid arthritis susceptibility genes, this program proposes an innovative method of specific downregulation of autoimmune reactions. Immune response genes coupled to autoantigenic peptides will be used to generate regulatory T cells. A general regulator of immune reactions is Vitamin D. This vitamin has long been known to regulate calcium homeostasis but recent discoveries have suggested that it may also have important immune regulatory properties for both innate and specific autoimmunity. One of the projects proposed will determine, in collaboration with the other projects, the ability of a vitamin D analog that does not have the hypercalcemic property of vitamin D to regulate both spontaneous and induced arthritis. All of the projects in the Program will use a core dedicated to providing uniformly high quality standardized analyses to each project. This will enable comparison of data among the projects and realize substantial savings by centralizing commonly used methods. In addition the core will develop an independent scientific direction by developing a novel method for both evaluation of the presence and severity of arthritis with the potential for use as a targeted delivery system for therapeutic compounds. To expand the research base of the VAMC, each of the component projects has initiated collaboration with an external expert who will provide addition insights into the proposed experiments. These collaborative efforts will serve to generate an atmosphere of intellectual excitement and rapport.!